This invention relates generally to flat panel display devices and particularly to a shielded electron beam guide assembly for such devices.
U.S. Pat. No. 4,330,735 discloses a beam guide assembly for a flat panel display device in which a pair of beam guide meshes, a focus mesh and an acceleration mesh are held in a spaced parallel relationship by a plurality of insulative supports which are spaced along the edges of the meshes for the full length of the assembly. Beam guide assemblies fabricated in accordance with the disclosure of the referenced patent are advantageous because the meshes of which the assembly is comprised are accurately and permanently held in the desired space relationships. Also, the lengths of the supports can be carefully controlled thereby assuring uniform spacing of the mesh assemblies from the baseplate upon which they rest. However, some difficulty can arise because the transverse dimension of the mesh assemblies typically is small, for example in the order of 1.0 to 1.25 inch (2.54 to 3.175 cm). Accordingly, in a color display device utilizing three electron beams, the two outside beams are in the close proximity of the insulative supports. For this reason, stray electrons from the beams, or from other sources such as field emission, sometimes impinge upon and negatively charge the insulative supports. Such charges adversely affect the trajectories of electron beams which are traveling toward the screen. Additionally, electric fields and components external to the beam guide assemblies can adversely affect the trajectories of electrons within the beam guide assemblies.
The instant invention overcomes this difficulty by the provision of shields which maintain uniform electric fields within the beam guide assemblies and which prevent stray electrons from impinging upon the insulative support members thereby preventing the support members from becoming electrically charged.